Method of making slewing bearings for cranes and the like



Oct. 13, 1959 B. RICHARDSON ETAI- 2,998,069

METHOD oF MAKING sLEwING BEARINGS Fo cRANEs AND TEE LIKE Filed Oct. 29, 1956 2 Sheets-Sheet 1 llllsh l Inventors Oct. 13, 1959 B. mCHARDSON my 2,908,069

METHOD OF MAKING SLEWING BEARINGS FOR CRANES AND LIKE Filed Oct. 29, 1956 2 Sheets-Sheet 2 ltorneys NIETHOD OF MAKING SLEWING BEARINGS FOR RANES AND THE LIKE Bert Richardson and Norman Brocklebank, Hull, England, "assignors to Priestman BrothersLimited, Hull, Y England, a British company Application october 29, 1956, serial No. 618,924

z Claims. (C1. 29 i14s.4)

This invention relates to excavators and cranes and is particularly concerned with the method of making the bearing and pivotal mounting of the superstructure carrying the cab and jib upon an undercarriage or stationary structure.

Inthe conventional arrangement, the frame of the superstructure pivots o a centre pin or king post and is supported against tilting by horizontal rollers running in annular races concentric with the centre pin. The bearing upon which the superstructure rotates is subjected to a complex and varying system of forces including the dead weight of the excavator superstructure and front end equipment, the line of action of which varies with the type of front end equipment and, while the machine is working, producing varying tilting forces which also rotate as the superstructure is slewed. The digging action of excavators also produces horizontal loading and tilting moments.

According to the present invention the superstructure carrying the cab and the jib is pivoted to the under carriage or, other support by means of a bearing comprising two coaxial sets of tapered rollers, each running between opposite pairs of race surfaces arranged so that when seen in section the four surfaces constitute a quadrilateral within which the rollers run and in which the rollers of one set are interspersed with those of the other set with the axes of the rollers in one set transverse to those in the other and oblique to the vertical.

Y In general the rollers of one set will alternate with those in the other, but two or three or even more roller'sofqoneset may follow one another.

By reason ofthe operating conditions which obtain in a crane or excavator, the use of such a bearing has unexpected advantages in that instead of having to grind the race surfaces after they have been hardened, it is possible to machine them initially and to carry out the hardening process after the machining is complete. With normal bearings this is not possible owing to the slight distortions which may be caused by the hardening process. With a bearing for use in a crane or excavator, however, where the speeds of rotation are relatively low, minor distortions can be tolerated. Preferably, however, the racel surfaces are each formed on separate bearing rings secured together vertically in pairs. Any minor distortions of the individual rings therefore tend to be reduced to negligible dimensions when one ring is forced into contact with the other ring of the pair after the insertion of the rollers.

An example of excavator or crane in accordance with the invention will now be described in more detail with reference to the accompanying drawings in which:

Figure 1 is an outline view of part of the excavator or crane showing a slewing bearing partly in section;

Figure 2 is a sectional view of the bearing shown in Figure 1 to an enlarged scale;

Figure 3 is a sectional view corresponding to Figure 2 of a modilied form of bearing; and

Figure 4 is a perspective view of the bearing of Figure 3 with parts broken away.

In the outline view of Figure 1 the excavator or crane has a superstructure carrying the cab, part of which is shown at 1, and the jib, one end of which is shown at 2. These parts are mounted on the undercarriage 3 by means of a slewing bearing indicated generally at 4 and illus- .trated in more' kdetail in Figure 2. The bearing includes two pairs of opposite race surfaces 5 and 6 and 7 and 8. Tapered rollers 9 run between the race surfaces 5 and 6, while taperedrollers 10 run betweenthe race surfaces 7 and 8. These four surfaces thus constitute a quadrilateral with the axes of the rollers in one set transverse to those in the other. As shown, the axes of each of the two sets of rollers are at approximately 45 to the vertical, but this angle is not critical and may vary with the operating conditions.

The four race surfaces 6, 7, 8 and 5 are formed re- Y spectively on bearing rings 16, 17, 18 and 19 rwhich are secured together n pairs. The rings 16 and 18 are secured together by screws 20 seen in dotted outline in Figure 2 and also by further screws 21 which, in addition, secure-part of the superstructure seen in dotted lines at 1 to the bearing ring 18. The rings 17 and 19 are secured together by screws 24, lwhile further screws 25 secure the ring 17 to the undercarriage 3. The four rings are each produced as forgings or castings which are first roughed out and then have their race surfaces accurately machined by means of electronic copying. When the machining is complete the race surfaces are flame-hardened and tempered. It is found in practice that the hardness of the surfaces should lie in the region of 52 to 56 on the Rockwell C scale, the depth of hardening being strictly controlled.

The two pairs of rings are spigoted together as seen at 22 and 23 to prevent slipping or iidget between the rings when the bearing is unevenly loaded. The rings 17 and 19 are screwed firmly into contact with one another, a small sealing ring 26 being seated in a corresponding recess. The rings 16 and 18, however, are separated by means of steel shims 27 arranged between the screws, a small sealing ring 28 being located in a corresponding re, cess. In assembly shims of the peelable type are used which can be inserted without the removal of the ring. After the rings have been adjusted so as just to be in contact with the rollers, one or more shims are then removed until the required pre-loading stress is produced on the rollers. The thickness of shims removed to produce this pre-loading may vary between three and fifteen thousandths of an inch according to thedesign of bearing and the nature of the loading. This preeloading is a most important factor in the design of the bearing and prevents the rollers reacting on the race paths to produce pitting or brinelling due to vibration and shock loading. When the preloading has been achieved the bearing is dismantled, cleaned, packed with high pressure grease and reassembled with robust permanent shims of the required thickness.

Further somewhat larger sealing rings 29 and 30 are located in recesses in the side of the ring 17 and in the top of the ring 19 respectively. The sealing rings have slightly concave sides and when the bearing is assembled are maintained under slight pressure to maintain an eective grease seal against the side of the ring 16 and the underside of the superstructure 1. Inaddition to the seal 29, a grease-filled labyrinth 31 is provided as an additional precaution against the entry of water and dirt to the bearing. Grease is pumped in through a series of lubrication points 32. Initially the grease passes through an opening 34 filling any empty spaces between the rollers and the upper side of seal 29, Figure 2. When resistance is encountered the "grease kwill travel 'through opening 33 to ill the labyrinth 31.

As previously mentioned, the rollers 91 and lAQare tae'redahd'are'hld by iri'ean's'of caes L' A v so that each roller is in elct "c ntaihed in separate ew of lng.' l y A "Eaclrcage :consists vof an ppioiciriately 'sf "consisting of two plate'sgspot welded o" lier Y y with afcntral opening l36 for the rceptlonjof the `roller which 'is heldin position by inans "of vlugs The i'ndividual sections abut lagainst lone another .endto end, fssen fin'Figure 4, and thisl facilitates tner'ejady removal 'oiirfrn'gemen'tof individual'rollers v'nie/"ring '17 is formed inte'r'nal teleth which "es'h w'itlij'a slewing pinion "(s'etrV in vrirount'ed onavdiivens'hai't 2,"ex'tendig downwardly itrnthe `cab '1. When the pinion riflfisfv en it vruns around vthe ring of teeth 40cc'ausingrthe vsuperstruct'ui'e to rotate, andthus` provide the "requiredslewing"motion of 'the superstructure. p t l v j Y e modified bearing' of Figures S'ind 4 tliiers from Vthat of Figures l and 2'pi'irnarilyfin that the fof teeth for Yengagement with the slewigpinion is formed extrnally, asV 'seen'.atSG linstead of 'internally `inthe pre'- 'vio'u's construction. This leads to a'rnfiodiiicatin in the general design of the four-'bearing ringisfbt the race surfaces and therollers runningbetweeh fther i'ewid'enti'- C'al with those shown in Figure `2 and areindic'ated the 'san/1e lreference nur'n'e'rals. The race Surfcsu's, fand '8 areformed'onlbearin'g rings 53, 54, 51 and 52 respectivelyathe ring 54 carrying the teethZSO, V'as previously f mentioned. KK p Y Y The bearing rings 51 and 53 areheld 1together by screws shown dotted at 55 and 'by furtheruscrews 56 which alsokserve to secure the superstruc'tur tothe bear ing ring 53. The bearingi rings are "seV r'at'ed by seginental shirns 57 corresponding to the s'hiis "27 of 2., angdby a small sealing rin`gm58;

The bearing rings 52 and 54 ali-e held 'together by screws 59 being separated b'y'a 'small s ealingfringflll Further screws 61'secure the beariigrin'gSl tothe under carriage 3. The pairs of rings ar'e'spigoted together at6'2 and 63Y to prevent fidget. Y H w n n Further sealing rings 66 and 67 correspond with lthe rings 29 and 30 shown in Figure 2. ln'this lattercas'e, however, the sealing rings are accommodated in recesses Surfae the.' folli? Y0f Said ras@ erossasjectim, constituting 'a q' -piref' "to one another at rings positioned vertically above'onlan A ot er 1ns1 e first and secondV bearing" ings, s'ad r'st thifdbearing rings being (shapedto intertmwith `said second and fourth bearing Arings respectively 'by 'means of a spigot connection, each said bearing ring having an annular race faces, when bearing is i'eassenbled.

References Cited inthe le of this pit UNITED STATES PATENTS 1,235,116 Coppage Tuly` 31, `1'917 2,040,741 Heks May `Y12; 1936 2.220137 scott m29; 11949 2,313,084 Manly Maf; "9, 31943 Y2,545,122. Thompson r13 11951 l2,628,137 Ashram Een. '10, 1953 2,708,767 Y Dtrgr; My 22g-19515 

